Citation or identification of any reference herein, or any section of this application shall not be construed as an admission that such reference is available as prior art to the present application. The disclosures of each of these publications are hereby incorporated by reference in their entirety in this application, and shall be treated as if the entirety thereof forms a part of this application.
In the United States, conventional influenza types A or B viral epidemics can cause illness in 10% to 20% of people and are associated with an average of 36,000 deaths and an estimated 120,000-200,000 hospitalizations per year (estimates vary to do complications of pneumonia). In the advent of a highly pathogenic avian type influenza pandemic, the potential for severe morbidity and mortality will be substantially higher, and will occur during a time where the healthcare system is overburden. Many people will receive prior vaccination. During conventional epidemics, those receiving a vaccine do so with the presumption that 1) the vaccination will be successful and 2) that the vaccine matches the emerging pathogenic strain. Prior to, and during, a pandemic of highly pathogenic avian influenza or other influenza strain, those two assumptions may be inaccurate, yet, at the present time, there is no readily available means for people to determine if these immunization criteria have been met.
Currently established serological methods for detection of antibodies to influenza are necessary to conduct clinical trials of influenza vaccination, but are technical in nature, not accessible to the general public, and do not compare results for different antigens that would allow determination of which vaccine may have been successful when one or more vaccines has been administered (Cheng et al., 2008, Serologic and genetic characterization analysis of a highly pathogenic influenza virus (H5N1) isolated from an infected man in Shenzhen, J. Med. Virol. 80: 1058-1064; Katz et al., 1999, Antibody response in individuals infected with avian influenza A (H5N1) virus and detection of anti-H5 antibody among household and social contacts. J. Infect. Dis. 180: 1763-1770; Rowe et al., 1999, detection of antibody to avian influenza A (H5N1) virus in human serum using a combination of serologic assays, J. Clin. Microbiol. 37: 937-943).
Such methods determine the immune response, or seroconversion, in the host, which are specific antibody responses to vaccination or post viral infection, and should not be confused with diagnostics that determine the presence of the physical virus particle during infection such as described by Zambon and Ellis, 2001 (Molecular methods for diagnosis of influenza International Congress Series 1219: 267-273).
Following influenza vaccination performed in mid-1997 a study was performed by de Jong et al., (2001, Antibody responses in elderly to influenza vaccination in case of an antigenic mismatch, International Congress Series 1219: 707-711) wherein sera were obtained from vaccinees of various ages, including residents of nursing homes over 60 years of age. As a surrogate marker for induction of protection by influenza vaccination, they studied the haemagglutination inhibition (HI) antibody response of the vaccinees to vaccine and epidemic strains of the three (sub)types A(H3N2), A(H1N1), and B. Statistical methods included the paired t-test, the McNemar c2-test, the one-way ANOVA, the Pearson c2-test, and a “minimum-maximum” analysis, newly developed by Dr G. Lüchters from Bonn. In accordance with usual practice, the “50% protective threshold” of HI antibodies was set at 1:40 (Periera et al., 1972, Prevalence of antibody to current influenza viruses and effect of vaccination on antibody response. British Medical Journal 4:701-703).
In the influenza season of 1997/1998, a major antigenic mismatch of the H3N2 vaccine component occurred. They found that the vigor of immune responses declined at higher ages. Sera from influenza vaccinees was further used to assess the magnitude of this effect in case of an antigenic mismatch. At advanced age, the homologous antibody response was lowered, starting above 60 years. In addition, they found that the cross-reactivity of the formed antibodies to the drifted field virus decreased with age, starting above 70 years. They concluded that effect of ageing on the induction of “protective” titres (≧40) of HI antibodies against an emerging deviant strain can be severe, and that in the 1997/1998 season, in those above 80 years of age, the percentage of vaccinees acquiring such titres against the major epidemic H3N2 virus was only about 15%.
In the study by Keren et al., 2005 (Failure of influenza vaccination in the aged, J. Med. Virol. 25: 85-89), they found that in a cohort of 127 nursing home residents aged 60-98 years vaccinated during the winter of 1985-86 with the A-Chile 1/83 (c), A-Philippines 2/82 (p), and B-USSR (B) commercial influenza vaccines, that before vaccination 40%, 23%, and 69% were susceptible to influenza Ac, Ap, and B, respectively [hemagglutinin inhibition (H.I.) titer <1:40] and that one month following initial vaccination, 32 patients [25%] remained unprotected against two or all three vaccine strains. The unprotected patients were revaccinated with the same influenza vaccine and followed up. At five months 11%, 19%, and 23% of the initial cohort were still unprotected against Ac, Ap, and B strains, respectively. They conclude that two conventional influenza vaccines administered one month apart leave unprotected 30% of healthy elderly people who are initial influenza vaccine failures.
Physicians have long believed that the elderly often fail to generate a sufficient immune response for protection when given a standard seasonal flu shot, as illustrated in the studies by de Jong et al., 2001 and Keren et al., 2005 described above. About 90 percent of the estimated 36,000 people who die from flu-related causes in the United States each year are 65 and older, and account for an estimated 120,000 hospitalizations. Although fewer children die from influenza, infection results in an additional 20,000 hospitalizations per year, with a total up to 200,000 resulting from all influenza infections. Unfortunately, of those who are vaccinated with conventional vaccines, there is no convention regarding determination of the extent to which the vaccination was successful. The fact that the vaccine may not be antigenically matched to the emergent seasonal vaccine further compromises the overall protective effect on the population. Despite the obvious “leap-of-faith” in being vaccinated without determining effectiveness, there has been no apparent movement toward developing a diagnostic test that would inform a patient whether they were adequately protected.
Highly pathogenic H5N1 avian influenza presents a number of similar complications as conventional influenza as well as new challenges in effectively protecting individuals within a population. First, the vaccines for H5N1 have not been subjected to an epidemiological challenge for effectiveness (i.e., an actual pandemic); surrogate markers such as the level of anti-influenza antibodies are used to gauge effectiveness. It is generally accepted that an antibody level of 1:40 (higher numbers indicate better protection) is required to give 50% protection for a standard influenza. A number of vaccine makers have increased production of conventional-type vaccine for H5N1, and a number of biotechnology companies have introduced new approaches to generating novel vaccines and have shown the ability to generate anti-H5N1 antibodies, including the use of virus-like particles (Pusko et al., 2010, Recombinant H1N1 virus-like particle vaccine elicits protective immunity in ferrets against the 2009 pandemic H1N1 influenza virus, Vaccine, 28:4771-4776) or influenza proteins produced in tobacco plants (Lico et al., 2009, Plant-produced potato virus X chimeric particles displaying an influenza virus-derived peptide activate specific CD8+ T cells in mice. Vaccine, 27:5069-76). However, given the highly pathogenic nature of the H5N1 avian influenza (50-80% mortality), an antibody level of 40 may not be effective at all, at least on its own. Thus, a remarkably novel situation exists in terms of the number of different vaccine manufacturers and types of vaccines that may be available for H5N1 for which the ramifications have not been explored. This situation will also be complicated by differences in the antigens used to prepare the vaccine and their match to the emerging pathogen or pathogens. In countries where multiple types of vaccines are available, it seems probable that people will question the efficacy of individual vaccine types, which would require diagnostic testing in order to determine; a situation that has not been previously recognized and for which no solution has been proposed. The potential ineffectiveness of a single vaccine may lead many to seek a second vaccination using the same or an alternative vaccine type. While it would seem desirable to proceed to multiple vaccinations without testing, only through testing will the individuals within the population know if and/or when a vaccine or set of vaccines has been effective for them personally and will the medical field know which vaccines and/or combination of vaccines are effective within a population. The consequence of an unsuccessful vaccination and infection by H5N1 may be death, dramatically skewing the cost-benefit ratio analysis. Furthermore, in the advent of a shortage, the availability of a second vaccine for those already receiving an initial injection may not be justifiable without a diagnostic test indicating its necessity, even if the test were more expensive than the vaccine itself.